Otolith microstructure of young-of-year Atlantic silversides (Menidia menidia) from Mumford Cove during 2015

Back-calculated age, hatch date, length-at-age, growth rate, and experienced temperature of young-of-year Atlantic silversides (Menidia menidia) collected during 3 successive collections in Mumford Cove, CT in fall 2015.

To estimate the thermal history of October YoY we used continuous temperature data recorded by a Manta Sub2 probe (Eureka© Water Probes) at our study site. Three small gaps in the record (<8 days) were linearly interpolated. Daily temperatures during a larger data gap (34 days, 18 June -22 July) were estimated via linear regression between the Mumford Cove dataset and temperatures in nearby Niantic Bay (2015-2016) that were strongly correlated (TMumford= 1.07*TNiantic -0.54 r²= 0.92, F = 6024.9, p < 0.001). Average daily temperatures were then linked to the corresponding day of increment formation for each individual. To quantify the thermal dependency of larval growth in October YoY, we calculated the mean experienced temperature during the first 30 dph for each individual and correlated it to its mean daily growth rate over the first 30dph (GR30) and its back-calculated TL at day 30 post hatch (TL30, a proxy for the end of the larval stage).

Processing Description
Data Processing: The proportion of females (Nfem/Nfem+male) per 10 mm TL class in the otolith sample was used to derive sex-specific TL distributions of the population sample (beach seine), assuming sexes being randomly sampled within each TL class. Similarly, otolith-derived hatch distributions were scaled to population by applying a scale factor (SF) to each individual based on the relative frequencies (RF) of each 10 mm TL class in the population vs. otolith sample for each collection (SF = RFpopulation/RFotolith).
Only for YoY survivors from October, individuals were grouped into each of four bi-weekly hatch intervals that were chosen based on sample size and the known semi-lunar spawning periodicity of silversides. TL-at-age was back-calculated for each individual over the entire increment record (99-148dph) with the biological intercept method and an assumed length at hatch of 5 mm.
Problem Report: As detailed in the corresponding publication, a central objective was to determine whether ages in older young-of-year Atlantic silversides could be reliably determined. Because this was found to be the case only for individuals sampled during October, but not during subsequent collections in November and December, back-calculated ages, hatch dates, length-at-age, or growth rates are only given for individuals collected in October.
[ to anthropogenic environmental change. It will combine environmental monitoring with advanced experimental approaches to characterize early and whole life consequences of acidification and hypoxia in the Atlantic silverside (Menidia menidia), a valued model species and important forage fish along most of the US east coast. Experiments will employ a newly constructed, computer-controlled fish rearing system to allow independent and combined manipulation of seawater pCO2 and dissolved oxygen (DO) content and the application of static and fluctuating pCO2 and DO levels that were chosen to represent contemporary and potential future scenarios in productive coastal habitats. First CO2, DO, and CO2 × DO dependent reaction norms will be quantified for fitness-relevant early life history (ELH) traits including pre-and post-hatch survival, time to hatch, post-hatch growth, by rearing offspring collected from wild adults from fertilization to 20 days post hatch (dph) using a full factorial design of 3 CO2 × 3 DO levels. Second, the effects of tidal and diel CO2 × DO fluctuations of different amplitudes on silverside ELH traits will be quantified. To address knowledge gaps regarding the CO2-sensitivity in this species, laboratory manipulations of adult spawner environments and reciprocal offspring exposure experiments will elucidate the role of transgenerational plasticity as a potential short-term mechanism to cope with changing environments. To better understand the mechanisms of fish early life CO2-sensitivity, the effects of temperature × CO2 on pre-and post-hatch metabolism will be robustly quantified.
The final objective is to rear silversides from fertilization to maturity under different CO2 levels and assess potential CO2-effects on sex ratio and whole life growth and fecundity. Related